Scientists have uncovered genetic variants that increase the risk of attention deficit hyperactivity disorder (ADHD) in research that experts hope could lead to a better understanding of the condition.

ADHD is thought to affect about 2.5% of adults and about 5% of children worldwide. Concerns have been raised that the neurodevelopmental disorder is under-diagnosed and under-treated in the UK.

“We know that it is highly heritable,” said Prof Anders Børglum, co-author of the research, from Aahus University in Denmark. “Among all the causes that can lead to ADHD, genetic factors account for between 70% and 80%.”

However, researchers say it has been difficult to find specific genetic variants linked to ADHD. Børglum said this was because many genes were thought to be involved in the condition, each increasing the risk by a tiny degree.

Now, by scanning the genomes of more than 55,000 individuals, more than 20,000 of whom had a diagnosis of ADHD, Børglum and a large international group of researchers say they have identified 12 particular regions in the genome where changes increase the risk of ADHD.

“We are extremely excited about these findings … we have been looking for this for ages,” said Børglum.

He said changes in the regions discovered accounted for less than 1% of the genetic risk for the condition. “Those 12 regions are just representing the tip of the iceberg,” he said, noting there were likely to be thousands more to be discovered.

The team says the findings could help shed light on the biological mechanisms behind ADHD, potentially aiding the development of new drugs.

The team’s work, published in the journal Nature Genetics, supports previous studies that found that a wider pattern of genetic variants more commonly seen in those with ADHD was similar to that seen in people with other conditions including depression and insomnia.

The researchers say the study supports the idea that ADHD is an “extreme expression” of traits found throughout the population.

Michelle Beckett, the chief executive of the charity ADHD Action, said the results of the new study were exciting and could lead to a better understanding of the biology of the condition.

But she said diagnosing ADHD on the basis of the newly discovered genetic variants alone would be unwise since it was not clear that everyone diagnosed with ADHD would have them.

“We have only officially diagnosed the tip of the iceberg of individuals globally with ADHD, and further gene research is highly likely to uncover more variations that may be also responsible,” she said.

Børglum said the study could help destigmatise the condition and tackle the guilt and blame parents often encounter when their child has ADHD.

While some have previously argued that discovering a biological basis for conditions such as ADHD might not help to reduce stigma, Beckett said the new findings could have a positive effect in showing the condition is real.

“ADHD faces incredible stigma and discrimination and denialism,” and was often thought to be an excuse for poor behaviour, despite the impact the condition could have on an individual’s education, health and work, said Beckett. “This [study] almost gives us a validation, if you like, in the eyes of the people on the street and also the popular press.”